The invention relates to securing cables to an electrical box.
When electrical cables are inserted into an electrical box, such as a junction box, metal or plastic traps are used to secure the cables to the box. This prevents longitudinal forces from stressing wire connections in the box and separating the connections.
When a metal trap is used, a pre-punched knockout in the side of the box is removed and the metal trap is inserted in the resulting hole. The trap then is secured in place using a threaded nut in the interior of the box. The electrical cable is then threaded through the trap. Next, the wires of the cable are stripped and any excess cable is backed out of the electrical box. Two screws on the metal trap then are tightened to secure the electrical cable in place. Finally, the wires of the cable are connected and a cover is placed on the electrical box.
When a plastic trap is used, a pre-punched knockout is removed, and the plastic trap is inserted into the hole from which the knockout was removed. The cable then is inserted into the plastic trap. The wires then are stripped and connected. Finally, the cover is placed on the electrical box. Of course, the wires can be stripped before being placed into the plastic trap.
A representative electrical cable in both of these examples is a Romex cable, also known as non-metallic sheathed cable (type NM-B). Such a cable includes multiple conductors and an outer plastic protective sheath.
In both examples, an external trap is positioned in a knockout hole to ensure that the electrical cable remains in place.
In one general aspect, an invertible side insertion trap is designed to be inserted into an opening in an electrical box and to accommodate at least two different sizes of cable or wire depending on an orientation of the trap relative to the opening. The invertible side insertion trap includes a base, a first arm and a second arm. The first arm extends from the base and includes a first mating portion for mating with a first side of the opening in the electrical box. The second arm extends from the base. The arms define a passage having a first width for permitting insertion of a first cable or wire size between the arms when the trap is oriented in a first orientation with the first mating portion aligned with the first side of the opening. The passage has a second width for permitting insertion of a second cable or wire size between the arms when the trap is oriented in a second direction with the first mating portion aligned with a second side of the opening.
Implementations of the invertible side insertion trap may include one or more of the following features. For example, the second arm may include a second mating portion for mating with the second side of the opening in the electrical box. The first mating portion may be configured to mate with the first side of the opening in the electrical box but not to mate with the second side of the opening in the electrical box. The second mating portion may be configured to mate with the second side of the opening in the electrical box but not to mate with the first side of the opening in the electrical box. The first mating portion may include a raised portion that extends from a surface of the first mating portion and the first side of the opening may include a region that is shaped as a negative of the raised portion. The raised portion that extends from the surface of the first mating portion may be configured not to fit within the second side of the opening of the electrical box.
The second mating portion may include a first raised portion extending from a surface of the second mating portion and a second raised portion extending from the surface of the second mating portion, and the second side of the opening may include a region that is shaped as a negative of the raised portion. The first raised portion and the second raised portion that extend from the surface of the second mating portion do not fit within the first side of the opening of the electrical box.
The arms may include teeth that protrude into the first passage and the second passage. The first arm may include a raised portion that extends from one surface of the first arm and the second arm may include a raised portion that extends from an opposite surface of the second arm.
In another general aspect, a system for retaining at least two different sizes of cables or wires in an invertible side insertion trap in an electrical box includes an electrical box and an invertible side insertion trap. The electrical box includes a first wall and a pair of additional walls connected by the first wall, with the first wall including at least one opening. The invertible side insertion trap includes a base and a pair of arms defining a passage. The arms and the opening are configured such that the passage has a first width when a first arm is positioned adjacent a first side of the opening and a second narrow width when the first arm is positioned adjacent a second side of the opening.
In implementations of the system, the invertible side insertion trap can have any of the features of the invertible side insertion trap described above.
The invertible side insertion trap provides considerable advantages. For example, using a single trap, wire and cable of different sizes can be retained in the trap. This reduces the number of parts needed when wiring electrical boxes.
In another general aspect, a side insertion trap for retaining cable or wire includes a base and two arms. The arms extend from the base to define an opening between the arms for permitting insertion of a cable or wire between the arms. A pair of jaws extends from the arms. Each jaw includes at least one tooth oriented in a direction towards the opposite tooth.
Implementations of the side insertion trap may include one or more of the following features. For example, the arms and the jaws may define a passage and the teeth may extend into the passage. Each jaw may extend from the arms at an angle to define a narrowing of the passage. The teeth may have a rectangular shape and define a surface oriented in the direction of the passage. The surface may include at least one protrusion and may include a textured surface. The teeth also may have a rounded or an angled shape.
In another general aspect, an electrical box includes at least one integral side insertion trap for retaining cable or wire. The electrical box includes a first wall including at least one opening and a pair of additional walls connected to the first wall. The integral side trap includes a pair of jaws that extend from the first wall on opposite sides of the opening.
Implementations of the side insertion trap may include one or more of the following features. For example, the jaws may define a passage and teeth may extend into the passage from the jaws. Each jaw may extend from the opening wall at an angle to define a narrowing of the passage. The teeth may have a rectangular configuration and may define a surface oriented in the direction of the passage.
The side insertion trap provides an inexpensive, labor saving, cable fitting for inserting and securing an electrical cable in an electrical box. The cable is laterally retained in the trap by a cover of the electrical box, and can be easily removed upon removal of the cover. Detents may be used to further secure the cable laterally.
By allowing lateral insertion of a wire or cable, the side insertion trap eliminates the need to thread the wire or cable through the trap. This permits insulation to be removed (and connections to be made) prior to insertion of the wire or cable into the trap. This, in turn, eases installation.
Other features and advantages will be apparent from the following description, including the drawings, and from the claims.